Patent ES-A-2232243, of the same inventor as the present invention, describes an orthodontic archwire bracket including a base body with a base for being fixed to a tooth, a bracket body with a slot for the archwire, and an adjustment mechanism based on a ball and socket joint coupling between said base and bracket bodies, wherein the base body defines a socket element and the bracket body defines a ball element. The bracket body is made of a material having shape memory due to a thermal effect, such that when the two coupled bodies are at a temperature below the body temperature they are capable of mutual movement, and when they are heated to body temperature the expansion of the bracket body locks the ball and socket joint coupling in a desired position, which allows adjusting the torque and the inclination of the archwire without needing to change the bracket.
Nevertheless, a drawback of this bracket of the mentioned patent ES-A-2232243 is that the bracket body is essentially solid, so it is economically costly due to the relatively high price of the shape memory material and the impossibility of making it functional. Another drawback is that the bracket body does not include a retaining element for retaining the archwire in the corresponding slot, which forces resorting to additional elements.
U.S. Pat. No. 4,243,387 discloses an orthodontic archwire bracket including a base body having a base for being fixed to a tooth and a bracket body having a slot for the archwire. The base body and the bracket body are coupled to one another by a ball and socket joint coupling, wherein the base body has an inner spherical surface portion and the bracket body has an outer spherical surface portion. A screw inserted through an opening of the bracket body and threaded to the base body is operable to lock or unlock said ball and socket joint coupling. However, the fact that the screw head is located at the bottom of a hollow portion of the bracket body below the archwire makes it difficult to reach it with a driving tool, and also the bracket body does not include a retaining element for retaining the archwire in the slot.
International patent application WO 03/000151 discloses an orthodontic archwire bracket comprising a base to which there is fixed a plurality of parts having respective slot portions which together define a slot for the archwire and cavities between the slot portions where there are housed C-shaped latches for retaining the archwire in the slot. The latches can optionally be made of a material having shape memory. Nevertheless, this archwire bracket does not include adjustment means for varying the angular position of the archwire with respect to the base and the torque transmitted by the latter to the bracket. Furthermore, said plurality of parts imposes onerous manufacturing and assembly tasks.